HVDC (High Voltage Direct Current)

Presented byM.VenkateshkumarHVDC Transmission Overview •Power System•Introduction of Transmission•Voltage classification •HVDC system•Advantages and Disadvantages•Types of HVDC Configuration •HVDC converter.•HVDC Transmission Simulation modelPower System1.Generation 2.Transmission 3.Distribution 4.Protection and Switchgear Transmission •HVAC Transmission •HVDC TransmissionClassification of voltage rating•Low voltage : below 1000V•Medium voltage :1 KV to 100 KV•High voltage:100 KV to 230 KV•Extra high voltage:>230KV•Ultra high voltage :above1000KV(IET)IEEE 141:1983 Clause 3.1.1.2First DC DynamoLong-Legged Mary Ann type early DC dynamo created and sold by Thomas Edison.First Three Phase AC alternatorThis one was created for the Electrical Exposition in Frankfurt, Germany in 1891.HVDC•TheHVDCtechnologyisusedtotransmitelectricpoweroverlongdistancesbyoverheadtransmissionlinesorsubmarinecables.•Itisalsousedtointerconnectseparatepowersystems,wheretraditionalalternatingcurrent(AC)connectionscannotbeused.HVDC TRANSMISSION OVERVIEW •ThemodernformofHVDCtransmissionusestechnologydevelopedextensivelyinthe1930sinSwedenatASEA.•EarlycommercialinstallationsincludedoneintheSovietUnionin1951betweenMoscowandKashira,anda10-20MWsystembetweenGotlandandmainlandSwedenin1954.•XiangjiaDam–Shanghai±800kVHVDC1907kilometers.7200MW.(WorldlongestHVDCtransmission)•ThesecondlongestHVDClinkintheworldiscurrentlytheInga-Shaba1,700km(1,100mi)600MWlinkconnectingtheIngaDamtotheShabacoppermine,intheDemocraticRepublicofCongo.HVDC Transmission in India S.No System /ProjectYear Supplier Power Ratting (MW)Voltage (KV)Line Length (Km)1Vindhy-Achal1989ASEA5002 x 69.7Back to BacK2Rihand -Delhi1991-1992ABB/BHEL750/15005008143Chandrapur-Padghe1998ABB/BHEL15005007364Talcher-Kolar2003Siemens200050014005Balia-Bhiwadi2009Siemens/BHEL2500500780HVDC in IndiaUpcoming ProjectEvaluation of Technical ConsiderationHVAC -HVDC•Stability Limits•Voltage Control•Line Compensation•Problem of AC Interconnection•Ground Impedance Major Advantages1.Ifthecostofconverterstationisexcluded,thedcoverheadlinesandcablesarelessexpensivethanaclinesandcables.2.Adclinkisasynchronous.3.Thecoronalossandradiointerferenceareless.4.Fordcline,reactivepowercompensationisnotneeded.5.Thelinelengthisnotrestrictedbystability.6.Theinterconnectionoftwoseparateacsystemsviaadclinkdoesnotincreasetheshort-circuitcapacity,andthusthecircuitbreakerratingsofeithersystem.7.Thedclinelossissmallerthanforthecomparableacline.Major Disadvantages•Theconvertersgenerateharmonicvoltagesandcurrentsonbothdcandacsidesandthereforefiltersareneeded.•Theconverterconsumesreactivepower.Thedcconverterstationsareexpensive.Thedccircuitbreakersaredifficulttodesign.Types of HVDC Configuration 1. Monopolar link2. Bipolar link3.Homopolar linkHVDC linksMonopolar linkMonopolar •Monopolar link has a one conductor ( ground or sea return)•A Metallic return can also be used where concerns for harmonics and or /corrosion exist.•In application with DC cables (ieHVDC light)•A Monopolar link is normally operated with negative polarity.( less corona effect)Bipolar Bipolar •Undernormalload,negligibleearth-currentflows,asinthecaseofmonopolartransmissionwithametallicearth-return.Thisreducesearthreturnlossandenvironmentaleffects.•Whenafaultdevelopsinaline,withearthreturnelectrodesinstalledateachendoftheline,approximatelyhalftheratedpowercancontinuetoflowusingtheearthasareturnpath,operatinginMonopolarmode.•SinceforagiventotalpowerratingeachconductorofabipolarlinecarriesonlyhalfthecurrentofMonopolarlines,thecostofthesecondconductorisreducedcomparedtoaMonopolarlineofthesamerating.•Inveryadverseterrain,thesecondconductormaybecarriedonanindependentsetoftransmissiontowers,sothatsomepowermaycontinuetobetransmittedevenifonelineisdamaged.Homopolar linkHomopolar•Inthistypeoflinktwoconductorshavingthesamepolarity(usuallynegative)canbeoperatedwithgroundormetallicreturn.•Duetotheundesirabilityofoperatingadclinkwithgroundreturn,bipolarlinksaremostlyused.•Ahomopolarlinkhastheadvantageofreducedinsulationcosts,butthedisadvantagesofearthreturnoutweightheadvantages.Back to Back•HighVoltageDCtechnologyenablestheinterconnectionoftwoasynchronousACnetworks.e.g.50Hzand60Hz.•AnHVDCsystemtakeselectricalpowerinanalternatingcurrent(AC)systemandconvertsitintohighvoltagedirectcurrent(DC)usingaconverterstation.•ItthentransmitstheDCtoaremotesystem,whereitisconvertedbackagaintoACbyanotherHVDCconverterstation.•Aback-to-backHVDCarrangementisusedwhentwoasynchronousACsystemsneedtobeinterconnectedforbulkpowertransmissionorforACsystemstabilizationresons.•InanHVDCback-to-backstationtherearenooverheadlinesorcablesseparatingtherectifierandtheinverter,hencethetransmissionelectricallossesontheDCsidecanbeneglected.Inaback-to-backHVDC,theDCcurrentcanbekepthighandtheDCvoltagelow.•InordertooptimizethecostsofthethyristorvalvesaswellastheDCsideequipment,theDCcurrentiskeptashighasthestandardthyristorratingandvalve•coolingsystemcanhandlesafely.ThismeansthattheDCvoltagecanbekeptfairlylow,andisthuschoseninrelationtotheratedDCpower.Back to BackTower model Cost of HVDCApplications of DC Transmission•Underground or underwater cables•Long distance bulk power transmission•Asynchronous interconnection of ac systems•Stabilization of power flows in integrated power systemAnalysis of HVDC ConvertersINTRODUCTION•A HVDC system requires an electronic converter for its ability of converting electrical energy from ac-dc or vice versa. •There are basically two configuration•types of three-phase converters possible for this conversion processTypes of Converters •Current Source Converter (CSC), •Voltage Source Converter (VSC).Current Source Converter (CSC)Voltage Source Converter (VSC)Cont….•Duringtheperiod(about)1950-1990s,HVDCsystemsusedtheCSCconfigurationalmostexclusively.•ThetraditionalCSCutilizedthemercury-arcvalvefromtheearly1950stothemid-1970s,andthereafter,thethyristorvalveasitsfundamentalswitchingdevice.•From about 1990 onwards, the alternative VSC became economically viable due to the availability of new self-commutating high-power switches (such as GTOs and IGBTs) and the computing power of DSPs to generate the appropriate firing patterns.Cont…•ModernHVDCtransmissionsystemscanutilizeeitherthetraditionalCurrentSourceConverter(CSC)ortheVoltageSourceConverter(VSC)asthebasicconversionworkhorse.•Thetwoconvertersareactuallydualsofoneanother.Comparison of VSC and CSC On AC sideCURRENT SOURCE CONVERTER •Act as a constant voltage source •Require a capacitor as its energy storing device•Requires large Ac filters for harmonic elimination •Requires reactive power supply for power factor correction Voltage sources converter On AC side •Act as a constant current sources•Requires an inductor as its energy storing devices •Requires only a small AC filter for harmonics elimination •Reactive power supply is not required as a converter can operate in any quadrant. DC side CSC•Acts as a constant current sources •Requires an inductor as its energy storing devices •Requires DC filters •Provides inherent fault current limiting features DC sideVSC•Acts as a constant voltage sources•Requires a capacitor as its energy storing devices •Energy storage capacitor provide DC filtering capability at no extra cost•Problematic for DC line side faults since the charged capacitor will discharge into faultSwitchesCSC•Linecommutatedorforcedcommutatedwithseriescapacitor•Switchingoccursatlinefrequency•LowerswitchinglossesAC side VSC•Selfcommutated•Switchingoccursathighfrequency•HighswitchinglossesRating rangeCSC•0–550MWperConverter•Upto600KVRating range VSC•0–200MWperConverter•Upto100KVComparing characteristics of CSC and VSCHVDC Transmission with Voltage Source ConvertersReference books1.Dr.VijayK.Sood.,“HVDCandFACTSControllersApplicationofstaticConvertersinpowersystem”LONDON.2.AdamsonC.andHingoraniN.G.,“HighvoltagedirectcurrentPowertransmission”,(London)Garraway,1960Matlab model-HVDC TransmissionThank you